In recent years, various mobile communications using quasi-microwave bands via portable wireless communication apparatus such as mobile phones are in the spotlight, and there is an increasing need not only for voice communications but also for data, image, and other types of communications. Therefore, the shapes of casing for portable wireless communication apparatus are diverse, depending on individual applications for use, such as long, straight types and folding types. As antennas mounted on portable wireless communication apparatus of these types, those that can be extended when in use and can be retracted when not in use are in actual use.
FIG. 1 is a view showing one example of a portable wireless communication apparatus having a conventional portable wireless communication apparatus antenna. The portable wireless communication apparatus shown in FIG. 1 comprises a wireless communication apparatus main body 112 having a printed board, a shield, a battery, a display portion, a key portion, and a microphone receiver, most of which are electrically conductive. It also includes a resin casing 111 for fixing the wireless communication apparatus main body 112, and a retractable and extensible antenna 113 mounted on the upper part of the casing 111.
The antenna 113 has a first antenna 114 having conductivity and a second antenna 116 including a coil disposed at the upper end of the first antenna via an insulator. An extension connection portion 114a that is connected to an antenna holder 117 fixed to the casing when the antenna is extended is provided at the lower end part (end part which is inserted into the casing) of the first antenna 114. A retraction connection portion 116a that is connected to the antenna holder 117 fixed to the casing when the antenna is retracted is provided at the lower end part (end part facing the first antenna) of the second antenna 116.
The antenna holder 117 is connected to the wireless communication apparatus main body 112 through a feeding terminal 118 including a spring and further connected to a matching circuit 119 in the wireless communication apparatus main body 112. When the antenna 113 is extended, the extension connection portion 114a is connected to the antenna holder 117 and the bar-shaped first antenna 114 is fed through the matching circuit 119 so that it operates as an antenna. At the same time, the second antenna 116 is not fed and therefore does not operate as an antenna due to the presence of the insulator 115.
In contrast, when the antenna 113 is retracted, the connection portion 116a is connected to the antenna holder 117 and so the coil-like second antenna 116 is fed through the matching circuit 119 to operate as an antenna protruding from the casing. At the same time, the retracted first antenna 114 is not fed due to the presence of the insulator 115, and does not operate as an antenna.
As described above, while being used, the antenna 113 is extended so that the bar-shaped first antenna 114 having good antenna characteristics can operate. When the wireless communication apparatus is carried around, the coil-like second antenna 116 operates with somewhat poorer antenna characteristics but smaller in size.
FIG. 2 is a view showing another example of a portable wireless communication apparatus having a conventional portable wireless communication apparatus antenna.
The portable wireless communication apparatus antenna shown in FIG. 2 includes a wireless communication apparatus main body 122 mostly constituted by conductive members, a resin casing 121 for mounting the wireless communication apparatus main body 122. It also includes a bar-shaped antenna 124 having connection terminals 124a and 124b at the upper and lower parts thereof, and an antenna holder 127 fixed to the casing 121 for holding the extended or retracted antenna 124 while at the same time connecting the antenna to a matching circuit 129 in the wireless communication apparatus main body 122 through a feeding terminal 128. The antenna further includes a retraction correction circuit 125 provided in the casing 121.
In this portable wireless communication apparatus, when the antenna is extended, the lower connection terminal 124b is connected to the antenna holder 127 and the antenna 124 protrudes, so that the antenna is fed through the matching circuit 129 in the wireless communication apparatus main body 122 to operate as a bar-shaped antenna.
In contrast, when the antenna is retracted, the upper connection terminal 124a is connected to the antenna holder 127 so that the antenna is fed through the matching circuit 129 in the wireless communication apparatus main body 122. At the same time, the lower connection terminal 124b is connected to the retraction correction circuit 125 in the casing. The retraction correction circuit 125 corrects impedance variations when the antenna is placed adjacent to the wireless communication apparatus main body 122 in the casing. Accordingly, it is possible to use the same matching circuit 129 not only when the antenna 124 is extended but also when retracted.
In recent years, there is a strong need for portable wireless communication apparatus to transmit not only voice but also data, images, and the like, and thus diversified casing shapes suitable therefor are needed. In the meantime, in order to increase the transmission speed and subscriber capacity, wider band communications are desired. To meet these requirements, such an antenna as is suitable for various casing shapes, has no protruding part when retracted, and has excellent portability and wideband characteristics when retracted is required.
In the case of the portable wireless communication apparatus shown in FIG. 1, the second antenna including a coil protrudes out of the casing when the antenna is retracted, causing a nuisance when the portable wireless communication apparatus is carried in a pocket or the like. Further, when the antenna is mounted to a broad casing like a notebook PC or a PDA, the antenna protrudes even when retracted, thus causing a remarkable damage to portability. It is necessary to upsize the second antenna in order to achieve wider antenna bandwidths when it is retracted, and this also causes a remarkable damage to the portability.
The portable wireless communication apparatus shown in FIG. 2 has no protruding part when the antenna is retracted, as described above, so that it provides very excellent portability and is applicable to casings of any shape. However, while the antenna is retracted, the antenna must be placed adjacent to or surrounded by the wireless communication apparatus main body, etc. constituted by conductive members in the casing. Therefore, the antenna volume decreases and the frequency characteristics become narrower even if matching is achieved by a retraction correction circuit as in the conventional example.
The present invention has been achieved in view of the forgoing. It is an object of the invention to provide a portable wireless communication apparatus antenna that is completely retractable and suitable for diversified casing shapes, and that has wideband characteristics suitable for large capacity transmission.